1. Technical Field
The present invention relates to a liquid supply mechanism that supplies liquid to a liquid ejection head through a sub-tank of which the volume is changed in response to deformation of a diaphragm, and a liquid ejecting apparatus including the liquid supply mechanism.
2. Related Art
An ink supply mechanism that has main tanks such as ink cartridges and sub-tanks mounted on a carriage together with an ink jet head is known as an example of an ink supply mechanism of an ink jet printer. The sub-tanks are replenished with ink from the main tanks and the ink is supplied from the sub-tanks to the ink jet head during printing. JP-A-2012-111096 discloses an ink jet printer, or a liquid ejecting apparatus, that includes an ink supply mechanism, or a liquid supply mechanism, of this type.
In the ink supply mechanism in JP-A-2012-111096, a diaphragm pump is provided on the top of the sub-tanks. The pump includes a diaphragm that closes the top end of each sub-tank and a piston that is connected to the diaphragm. When the piston is pulled up through a rocking lever, the volume of the sub-tank is increased, thereby causing a negative pressure state. Ink is then suctioned into the sub-tank. When the lever is released after ink replenishment and the piston is allowed to move freely, the piston is pushed down by the pressing force of a pressure spring, thereby causing a pressurized state inside the sub-tank. Thus, pressurized ink can be supplied from the sub-tank to the ink jet head.
In the ink supply mechanism in JP-A-2012-111096, the piston connected to the diaphragm moves up or down to increase or decrease the volume of the sub-tank. If the diaphragm is deformed into an unintended shape, inconveniences may occur. For example, when the piston is pushed down by the force of the pressure spring after ink replenishment, pressurized ink presses the diaphragm upward on the outer peripheral side of the piston. At this time, if the diaphragm expands upward, the piston is lowered by a corresponding amount. However, the amount of ink that can be suctioned at one time by a pump of this type corresponds to a difference in height for the piston. A lowered piston indicates that the amount of ink that can be suctioned at one time is reduced. In other words, if the diaphragm expands upward, there may be a disadvantage that an ink replenishing amount is reduced.
When the diaphragm excessively bends as a result of radially expanding outward by pressurized ink, the diaphragm does not form a normal rolled shape, and the bent portion of the diaphragm enters and is caught between the piston and a cylinder. As a result, the piston may lock. In addition, such a state of being caught may shorten the life of the diaphragm or cause poorly pressurized ink.